Date: Sat, 6 Oct 2018 21:21:04 +0300 From: Konstantin Belousov <kostikbel@gmail.com> To: freebsd-security@freebsd.org Subject: Re: [FreeBSD-Announce] FreeBSD Security Advisory FreeBSD-SA-18:12.elf Message-ID: <20181006182104.GS5335@kib.kiev.ua> In-Reply-To: <20181006173525.GC813@lena.kiev> References: <20180912054309.61C6B13269@freefall.freebsd.org> <20181006173525.GC813@lena.kiev>
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On Sat, Oct 06, 2018 at 08:35:26PM +0300, Lena@lena.kiev.ua wrote: > > Insufficient validation was performed in the ELF header parser, and malformed > > or otherwise invalid ELF binaries were not rejected as they should be. > > What is invalid in the /usr/local/share/google-earth/googleearth-bin > binary of the port google-earth-7.1.5.1557,3 ? > > FreeBSD 11.2-RELEASE-p4 Sep 27 GENERIC i386, the binary: > https://drive.google.com/file/d/1SgHk8ijSp2F9UcQGlx44psT832TdIEL0/view > > ~ $ googleearth > Invalid PT_INTERP > exec: ./googleearth-bin: Exec format error > ~ $ readelf --program-headers /usr/local/share/google-earth/googleearth-bin > > Elf file type is EXEC (Executable file) > Entry point 0x8048650 > There are 8 program headers, starting at offset 52 > > Program Headers: > Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align > PHDR 0x000034 0x08048034 0x08048034 0x00100 0x00100 R E 0x4 > INTERP 0x000134 0x08048134 0x08048134 0x00011 0x00011 R 0x1 > [Requesting program interpreter: /lib/ld-linux.so.2] As you see, the file delcares that file/memory length of the interpreter name' segment is 0x11 == 16 decimal. But the string does not end on byte 16, which is not NUL. We tighten the checks and do require that PT_INTERP string is valid by checking that it is NUL-terminated at the offset declared by the size.
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